1. Field of the Invention
The present invention relates to a method for producing L-valine by fermentation, and particularly relates to a method for producing L-valine with a microorganism constructed by a gene recombination technique.
2. Description of the Prior Art
Although a wild strain of Escherichia coli produced in the presence of a specific surfactant 1.42 g/dl L-valine (Japanese Published Examined Patent Application No. 21752/1966), most of wild strains do not produce L-valine in the medium. In order to render a wild strain capable of producing L-valine from carbohydrates, it has been necessary to induce artificial mutants from the wild strain. There are many known valine-producing artificial mutants. Most of the known valine-producing mutants are resistant to 2-thiazolealanine, and belong to the genus Brevibacterium or Corynebacterium.
Known valine high producers are Brevibacterium lactofermentum FERM-P 1963, which is resistant to 2-thiazole-alanine and requires for growth L-isoleucine (Japanese Published Examined Patent Application No. 116/1977) and which produced 2.51 g/dl L-valine, and Brevibacterium lactofermentum, KY 10614, which is resistant to S-2-aminoethyl-L-cysteine and which produced 3.05 g/dl L-valine.
It has however, become difficult to increase the yields of L-valine using the artificial mutation techniques. A need therefore, continues to exist for the development of novel methods for producing L-valine in high yields.